Concrete projection apparatus



Aug. 28, 1951 y B. MOLLER ETAAL" 2,565,696

CONCRETE PROJECTION APPARATUS Filed Oct. 22, 1947 INVENTOM' Buvili 40 a-oL $42 Lorpensive.

Patented Aug. 28, 1951 CONCRETE PROJECTION APPARATUS Bent Mller and ErikBjorn Nimskov, Copenhagen, Denmark Application October 22, 1947, SerialNo. 781,446 In Denmark October 25, 1946 8 Claims. 1

This invention relates to improvements in concrete projection apparatusand more particularly to such apparatus, known as cement or concreteguns, wherein an air flow is used for spraying a mixture of concrete andwater to a surface which is to be coated with a layer of concrete.

The main object of the invention is to provide means whereby the powerconsumption and hence the weight, dimensions and price of such apparatusmay be substantially reduced-as compared to the previously knownapparatus of this kind.

Another object is to provide a simplified construction of such apparatusby eliminating the need for certain devices previously used forintroducing the concrete mixture into a pressure conduit.

A further object is to provide means whereby waste of material issubstantially avoided.

Still a further object is to provide means whereby the quality of thecoating applied to the surface to be treated is substantially improved.

In the concrete guns heretofore used for applying a coating of concreteto surfaces of building structures such as walls, pillars or the likethe air flow employed for conveying the concrete from a receptacle tothe surface to be treated is produced by means of a source of compressedair, the working pressure required for the operation of such apparatusbeing generally of the order of 1-3 atmospheres. special means must beprovided for introducing the granular substance comprising a mixture ofsand and cement into a pressure conduit, one end of which is connectedto the said source of compressed air thereby producing an air flowthrough the said conduit, the other end of said conduit terminating in agun adapted to project the mixture of air and concrete with the additionof a water jet towards the surface to be treated.

The use of compressed air for producing a concrete carrying air flowinvolves various drawbacks. In the first place, the weight, dimensionsand initial cost of the apparatus are determined by the working pressurerequired for its operation and. since this pressure, as stated, shouldbe of the order of 1-3 atmospheres, such apparatus inevitably becomesrelatively heavy, large and ex- Secondly, the fact that the receptaclecontaining the mixture of cement and sand is subjected to atmosphericpressure, whereas a suitable working pressure must be maintained in theconduit leading from the receptacle to the gun at the other end thereof,special devices such as sluicing members are required for introducingthe concrete mixture from said receptacle into Moreover, in suchapparatus said pressure conduit. Thirdly, such apparatus require fortheir operation a relatively large excess of air relative to the amountof granular substance conveyed through the pressure conduit whichnecessitates that the gun must be held at a relatively large distancefrom the surface to be coated, thereby involving a comparative waste ofmaterial and causing inferior quality of the coating produced owing tothe formation of bubbles therein.

According to the present invention these drawbacks are overcome byeliminating the source of compressed air in concrete projectionapparatus and using instead thereof a suction conduit for producing anair flow which is utilised to convey the mixture of sand and cement fromthe receptacle containing said mixture to the surface to be coated bythe concrete jet projected there- While the accompanying drawings andthe description which is to follow, constitute a disclosure of thepreferred embodiments of the invention, it will be understood thatvarious changes may be made within the scope of what is claimed:

In the accompanying drawings:

Fig. 1 is a diagrammatic view of our concrete projection apparatusillustrating the various instrumentalities which control the operationof the same, the upper parts of the figure being shown in a somewhatenlarged scale.

Fig. 2 is an enlarged sectional side view showing details of oneembodiment of the invention.

Fig. 3 is a similar sectional side view showing details of anotherembodiment of the invention.

Fig. 4 is a vertical sectional view taken on the line IV-IV in Fig. 3.

Fig. 5 is a sectional side view similar to that of Figs. 2 and 3 showingdetails of a third embodiment of the invention.

Fig. 6 is a vertical sectional view taken along the line VIVI in Fig. 5.

Fig. '7 is a sectional side view in a still larger scale showing animproved construction of a nozzle for a concrete gun according to theinvention.

Referring to the drawings and more particularly to Fig. 1 thereof, l isa receptacle containing a mixture of cement and sand or the like, 2 is.a conduit leading from receptacle l to a gun 3 having a conical cap 4forming a nozzle at one end of said gun. 5 is a conduit communicatingwith the interior of gun 3 and connecting same to the suction end of arotary pump or blower 8. 6 is a water conduit communicating with theinterior of. gun 3 and leading to a faucet or water tap 1. 9 is aconduit leading from the pressure side of pump or blower 8 to receptacleI. I is a prime mover, for instance a Diesel engine, coupled to bloweror pump 8.

In order to illustrate the details more clearly parts 3, 4, 6 and T inthe upper part of Fig. 1 are drawn in a somewhat larger scale than partsI, 8 and In in the lower part of this figure.

Fig. 2 illustrates the details of the gun 3 in one embodiment of theinvention. In this embodiment the gun 3 is made of a substantiallytubular body having a flange 23 at one end thereof. In this body anannular channel I is pro vided so as to leave a tubular member 24forming a second channel I? therein. Channels I5 and I2 communicate witha cylindrical chamber II adjacent one end of gun 3, and channel I5 isprovided with an extension |5a having an internal thread 25 at one endthereof. Similarly, the end of channel i2 is provided with a thread 22,said threads 25 and being adapted to connect the gun 3 to the suctionconduit 5 and conduit 2 of Fig. 1 respectively. The body of the gun 3 isfurther provided with a channel It adapted to be connected to the waterconduit 6 of Fig. 1 by means of a thread 25 and communicating with anannular chamber 23a within the flange 23 between said flange and atubular extension 3a of the body 3. An external cap 4 having acylindrical part 2| is mounted on the tubular extension 301. abuttingthe flange 23, said cap 4, 2| being mounted by means of a thread l9 in acylindrical part I411 of an internal conical cap M which is in its turnmounted on extension 311 by means of a thread The two conical caps 4 andi4 provide a nozzle for the gun 3 having an outlet 29. The annular spaceformed between caps 4 and i4 communicates through passages 29 in part 2|with the annular chamber 23a and hence with channel i6 and the waterconduit 6.

In the embodiment of the gun illustrated in Figs. 3 and 4 the main bodyof the gun comprises two members: an external tubular barrel 3' having aconical extension 4, and an internal tubular member 39 having a tubularextension 32, said members being screwed together by means of threads3|. The channel I2 having a threaded inlet 22' is substantially axiallydis posed within the tubular member 36, while the channel I6 is disposedobliquely with respect to channel l2 and terminates in the projection 32having a threaded inlet 25'. A projection 21 is arranged within channell2 adjacent the outlet of channel |6'. The annular chamber l5communicating with an extension 25b in a projection 33 is formed betweenthe external surface of member 3| and the internal wall of barrel 3. 28is the outlet of channel i2 communicating with chamber II.

In the embodiment illustrated in Figs. 5 and 6 the gun comprises a body3 having two substantially parallel external channels I2 and I5" withthreaded inlets 22" and 25" respectively. Intermediate said channels l2"and I5" is a third channel It" having threaded inlet 26 and an outlet 38in an extension 3 3 of the body 3" at one end thereof. A flange 34 isprovided at one end of body 3 and adapted to fasten an external cap 49having an outlet or orifice 39 by means of screws 35. The interior ofsaid cap 49 provides a substantially U-shaped passage between channelsI2" and l5".

Fig. 7 illustrates an improved type of nozzle adapted to be mounted on agun of the kind referred to. This nozzle comprises three consecutiveconical caps 4|, 42 and 43 each disposed with its outlet in air flowalignment with the inlet of the consecutive cap and extending into saidinlet so as to form annular spaces 41 and 48 between caps 4|, 42 and 42,43 respectively. The caps 4|, 42, 43 are screwed together by means ofthreads 43 and 44. The annular spaces 4'! and 48 communicate with theexterior of the nozzle through grooves 45 and apertures 43, said groovesand apertures being shown by way of example only, it being understoodthat any other means of providing such communications may be used.

The operation of the concrete projection apparatus and more particularlyof the gun pertaining thereto is substantially as follows:

By means of the pump or blower 8, Fig. 1, a subatmospheric pressure isproduced in the suction conduit 5 connected with suction channels |5a,i512 and |5, |5', and I5 in Figs. 2-6 as the case may be. Thereby an airflow is produced in the concrete conveying conduit 2 leading fromreceptacle to channel l2, I2, or I2" in either of the embodimentsillustrated in Figs. 2-6. This air flow will cause the dry granularsubstance comprising for example a mixture of cement and sand to beextracted from receptacle I and conveyed into channel I2, |2, or l2"within the gun 3, 3', or 3" where it is mixed with a water jet passingthrough conduit 6 and channel Hi, It, or l6" thereby producing a wetconcrete mixture which, partly owing to the inertia of the granularsubstance and partly as a result of the action of the water jet, isprojected through apertures 29, 29' or 39 onto the surface to betreated. In the embodiment shown in Fig. 2 the amount of water flowingthrough channel It may be adjusted by means of the adjustment screw 24aand similar arrangements may, of course, be provided in the embodimentsshown in Figs. 3 and 5.

In the embodiment of the gun illustrated in Fig. 2 the actual mixture ofthe dry substance derived from receptacle with a Water jet derived fromthe source 1 takes place immediately outside the outlet 29, where aconical film of water 5| is formed owing to the passage of the waterflow from channel |6 through chamber 23a, grooves 2|! and the annularspace H between cones 4 and M. This water film 5| has the doublefunction of providing a thorough mixture of water and cement and sandgrains projected through channel l2, chambers H and |3 and the outlet29, and of providing a kind of screen which serves to prevent air fromthe outside of outlet 29 to be sucked therethrough and into the suctionchannel 15.

In the embodiment illustrated in Figs. 3 and 4 the water jet is injectedinto the channel l2 adjacent the projection 21 formed therein, whereby aprotective water film 49 is formed within chambers H and [3, thefunction of said film 49 being similar to that of 5| shown in Fig. 2.

In the embodiment illustrated in Figs. 5 and 6 channels l2" and I5"together with chamber 3? form a substantially U-shaped passage betweenconduits 2 and 5. The interior surface of cap 48 adjacent channel I2" ispreferably of parabolic shape. The function being air flow passingthrough the chamber 31 thereby becomes similar to that of the well knowncyclonic filters, the concrete mixture being projected through theoutlet 39 partly as a result of the cyclonic eifect in chamber 31 andpartly under the influence of the water jet ejected therethrough fromthe outlet 36 of channel 16 which is positioned substantially in fiowalignment with outlet 39 in cap 4E. The water jet forms a protectivefilm 49, within chamber 31 similar to that described with reference toFigs. 1 and 2.

The function of the nozzle construction illustrated in Fig. 7 is toprovide turbulent air currents within the spaces intermediate theconical caps 4|, 42 and 43. When a flow of concrete mixture is passingthrough the nozzle air will be sucked through grooves 45 and apertures46 thereby producing turbulent currents within the nozzle which willsubstantially prevent air from the outside of said nozzle to be suckedthrough the outlet of the external cap 43 and to pass in a backwardsdirection through the nozzle, i. e. in a direction opposite to the fiowof concrete mixture passing therethrough.

What we claim is:

1. A projection apparatus comprising in combination, hollow gun meansfor producing a spray of material and having a passage formed in theinterior thereof; a receptacle; a conduit communicating at one endthereof with said receptacle and at the other end thereof with saidpassage in said gun means; suction means communieating with the interiorof said gun so as to draw air through said first mentioned conduit andpassage, whereby material in said receptacle is sucked through saidfirst-mentioned conduit and passage; and a water conduit communicatingwith the interior of said gun means.

2. A projection apparatus comprising in combination a receptacle; hollowgun means for producing a spray of material and having a passage formedin the interior thereof; a material conveying conduit connected at oneend to said receptacle and at the other end to said passage; suctionmeans communicating with the interior of said gun means for producing asub-atmospheric pressure therein; and a water conduit communicating withthe interior of said gun means.

3. A projection apparatus comprising in combination, a receptacle; asuction conduit; a suction pump communicating at one end thereof withsaid receptacle and at the other end thereof with one end of saidsuction conduit; hollow gun means having its interior in communicationwith the other end of said suction conduit; a material conveying conduitcommunicating at one end with the interior of said receptacle and at theother end with the interior of said gun means; and water conduit meanscommunicating with the interior of said gun means for conveying a waterjet thereto.

4. An apparatus for the projection of a concrete mixture; comprising incombination, a receptacle; hollow gun means; a concrete conduitcommunicating at one end with said receptacle; suction conduit means; achamber in one end of said gun means; a first channel in said guncommunicating at one end with the other end of said concrete conveyingconduit and terminating in said chamber; a second channel disposed inthe interior of said gun means substantially coaxially with respect tosaid first channel and communicating with said chamber; meanscommunicating with said second channel and suction conduit means forconnecting said second channel to said suction conduit means; a firstconical cap at said one end of said gun formed with an orificecommunicating with said chamber within 'municating therewith; means forsaid gun; a second conical cap mounted in spaced relation to andsubstantially coaxially with said first cap about the exterior thereofso as to form an annular space between said caps; a third channel withinsaid gun communicating with said annular space; and means for connectingsaid third channel with a water conduit.

5. A gun for a concrete-projection apparatus comprising in combination,a tubular member having a conical cap at one end thereof; a first innerchannel within said tubular member; a chamber forming the terminal ofsaid inner channel at one end thereof; a concrete-conveying conduitcommunicating with the other end of said channel; a second channelobliquely disposed with respect to said first channel and comconnectingsaid second channel with a water conduit so as to inject a Water jetinto said first channel; a third channel disposed substantiallycoaxially with respect to said first channel; means for connecting saidthird channel to a suction conduit; projection means within said firstchannel, confronting the entrance of said second channel into said firstchannel and extending to said chamber, whereby said projection causesthe water jet to be sprayed within said chamber and said conical cap soas to substantially prevent air outside of said cap from being suckedtherethrough into the suction conduit.

6. A gun for a concrete-projection apparatus comprising in combination,a body having two substantially parallel external channels and a thirdinternal channel disposed therebetween; means for connecting one of saidexternal channels to a concrete-conveying conduit; means for connectingsaid second external channel to a suction conduit; means for connectingthe third internal channel to a water conduit an extension of said bodycontaining said third channel therein; a cap mounted at one end of saidbody and adapted to receive said extension; and an outlet in said capsubstantially in water fiow alignment with the outlet of said thirdchannel, the interior of said cap being shaped as a substantiallyU-shaped communication between said external channels.

7. A gun as claimed in claim 6, the internal surface of said capadjacent to the first external channel having a substantially parabolicshape.

8. A gun for the projection of a concrete mixture, comprising incombination, a nozzle at one end of said gun; conduit means connected tosaid gun for conveying the mixture toward said nozzle; said nozzlecomprising a plurality of conical caps having inlets and outlets, eachcap being positioned with its outlet in air fiow alignment with theinlet of the consecutive one of said caps and extending into said inletso as to form an annular space between said outlet and said inlet, andeach of said annular spaces communicating with the interior of saidcaps.

BENT MQ'DLLER. ERIK BJQRN NIMSKOV.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,223,586 Johnson Apr. 24, 19171,935,977 Geer Nov. 21, 1933 2,231,489 Anderson et a1. Feb. 11, 1941

